Model Output Discussion 25/11/2012 12Z onwards

[k19]

Excuse me Mods whilst I post this, might prove educational to some users.

Here is the difference between a trough and a shortwave. A shortwave is a kink in the isobars and ironically looks like a wave. A trough on the other hand is a shallow low and doesn't really have a defined pressure centre like a proper system.

In fact on the Trough Image you can see the difference between the trough circled and a Low pressure system just below it with the tightly packed isobars.

Good info, but worth noting if you're looking at N. hemisphere charts that shape would be reversed for the shortwave.

[Chris D]

There are now 3 minor models opposing the GFS and UKMO position. If the ECM backs the BOM, GEM and NOGAPS, then this could be over before it's begun - such is the finely balanced nature of the synoptics.

What? If this pattern dissolves into some sort of barlett or zonal scenario on the ECM I will eat my hat - the ECM will follow the other majors - eventually.

UKMO model for one, has been too consistent for me to think different. 500mb anom charts also do not support the pattern shown on the BOM etc.

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

Edited November 25, 2012 by Chris D

[PubliusEnigma]

Excuse me Mods whilst I post this, might prove educational to some users.

Here is the difference between a trough and a shortwave. A shortwave is a kink in the isobars and ironically looks like a wave. A trough on the other hand is a shallow low and doesn't really have a defined pressure centre like a proper system.

In fact on the Trough Image you can see the difference between the trough circled and a Low pressure system just below it with the tightly packed isobars.

Doesn't help you posted something from the southern hemisphere, so for most of the watchers here, the trough and short wave would appear the other way around.

We done for posting it.

In my experience you have the main primary Low pressure system. A typical example was the one that steamed through last night through the S SW and Wales and cleared

away earlier today. Often in a zonal flow a secondary low pressure forms usually following a similar track - this is called a secondary low or depression. A trough is usually

characterised by a 'V' shape in the isobar chart on a map. On the ground a trough or cold front often marks the centre line of the trough, with typically enhanced showery

activity through to a band of heavy rain, squally showers and thunderstorms, and even thunder-snow in mid winter. A trough is not to be confused with a mean trough which is

altogether different and is used to describe an area between two defined High pressure system or ridges. A short wave finally is often a smaller low that spins off a primary

low pressure usually from the edge of a warm front or the main low pressure system itself. Its often where the main low has left the jet stream and become slow moving, (as was the case a lot earlier this summer in the UK ) and a smaller disturbance breaks off, and gains a small rotation and separate identity to the primary low pressure system.

[IDO]

BOM is the Met taken further into FI. Thats why I never pay attention to the Met at 120 as you dont know where it is going. It appears to be heading for an Atlantic incursion (taken from BOM's later output):

At 120: http://modeles.meteo...om-0-120.png?12

At 162: http://modeles.meteo...om-0-162.png?12

Bearing in mind the GFS op is an outlier from next weekend throughout FI then there is still no strong indication that this first cold shot will be more than a pseudo-toppler.

At 186: http://modeles.meteo...om-0-186.png?12

At 210:

Edited November 25, 2012 by i'm dreaming of...

[Swave Snow]

There are now 3 minor models opposing the GFS and UKMO position. If the ECM backs the BOM, GEM and NOGAPS, then this could be over before it's begun - such is the finely balanced nature of the synoptics.

Further to this, a number of the GFS ensemble members look the same way as the 3 above, we have to think every possibility that ECM will go the same way.

I am afraid that these situations will always create HUGE difficulties for the Models ALL of them. We are seeing the Atlantic and the Artic in a very High pressure situations, quite a rare sight at any time in the winter. So I would follow Steve M and GP and Johnholmes and Nick Sussex and Chronomaniac and with all due respect I wouldn't just count on a weekend output as the be all and end all.

Edited November 25, 2012 by Swave Snow

[cyclonic happiness]

I apologise for my previous chart, that was the definition I take as being a shortwave?? Looks like I was wrong lol, but do so many people have to rub it in?? :-0

[Bolton67]

There are now 3 minor models opposing the GFS and UKMO position. If the ECM backs the BOM, GEM and NOGAPS, then this could be over before it's begun - such is the finely balanced nature of the synoptics.

Further to this, a number of the GFS ensemble members look the same way as the 3 above, we have to think every possibility that ECM will go the same way.

You also expected the ukmo 12z to back down and change it's tune. but i did not.

[Great Plum]

Big outlier by the gfs in Fi, downgrades the uppers for my area for next weekend, all part of the ride though would still much prefer the UKMO. Hope ECM improves this evening from the dirge of this mornings 0z

It's one of the colder runs but it is not an outlier, at any point...at least, not on the London ensemble...

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

[Ian Brown]

You also expected the ukmo 12z to back down and change it's tune. but i did not.

I expected the UKMO to complicate the issue with shortwaves, ok it did not. But we have now 3 models and many GFS ensemble members going for a wholly different scenario, so don't be too surprised if the ECM is very different to the GFS OP and UKMO at T144/168.

[snowmadchrisuk]

You also expected the ukmo 12z to back down and change it's tune. but i did not.

A lot of you worrying about the GFS ensembles , but if you lok out to +180 the Ensembles are Colder than the Op at least in the South (all I've checked) This just goes to prove the higher resolution is what is needed at the moment.

[PubliusEnigma]

BOM is the Met taken further into FI. Thats why I never pay attention to the Met at 120 as you dont know where it is going. It appears to be heading for an Atlantic incursion (taken from BOM's later output):

At 120: http://modeles.meteo...om-0-120.png?12

At 162: http://modeles.meteo...om-0-162.png?12

Bearing in mind the GFS op is an outlier from next weekend throughout FI then there is still no strong indication that this first cold shot will be more than a pseudo-toppler.

At 186: http://modeles.meteo...om-0-186.png?12

Even worse.

BOM is totally unreliable, one of the worst performing IMO at the moment, due to wild swings in output. It had been mirroring the UKMO, now its gone the reverse. The GFS was like the BOM is now, but has changed to how the ECM was a couple of days back. Meanwhile the ECM has reverted more akin to how the GFS had been performing in recent days and is similar to the latest BOM. UKMO has remained consistent. What will the 12z ECM do ?

[Mark Neal.]

Really are some doom ringers in here this evening. UKMO- was excellent and GFS was very good. Lets see what the ECM has to offer. Personally i think some of the models are struggling with the intensity of the block to our west and are under estimating it. I expect some more upgrades/ downgrades. But as we get closer things should start to improve if you want more than just a topper, this snap will last at least a few days IMO.

[Swave Snow]

I expected the UKMO to complicate the issue with shortwaves, ok it did not. But we have now 3 models and many GFS ensemble members going for a wholly different scenario, so don't be too surprised if the ECM is very different to the GFS OP and UKMO at T144/168.

The Ensembles have been all over the place these last three weeks, what are you suggesting? Those other models you refer to have also chopped and changed dramatically during the last three weeks. I don't think you can rely on the ensembles when blocking is playing a very strong hand.

[bradymk]

I expected the UKMO to complicate the issue with shortwaves, ok it did not. But we have now 3 models and many GFS ensemble members going for a wholly different scenario, so don't be too surprised if the ECM is very different to the GFS OP and UKMO at T144/168.

True but we do have the Met Office still confident on a blocked scenario throughout 10-15 day period which for me is a lot more encouraging than seeing the odd anomaly outputs from the smaller models and I do think the GFS ensembles are lacking some operational data for modelling this artic high, i could be wrong though. The cold is still not "certain" but it is now very likely, length still uncertain however the next 10 days at least look cold and blocked. Over to the ECM.

Matthew

Ps. ECM is poor, still requiring more runs, hoping for some good ensembles.

Edited November 25, 2012 by bradythemole

[cooling climate]

It seems as if some posters go looking for something to worry about when there isn't.

Onto the models and I would have thought the ECM will follow the UKMO out to t120 -

144 by now. Hopeing at the t144 range we see the ECM also develope the low further

east over the baltic which helps prop the high up instead of it drainning away se.

[Eskimo]

Doesn't help you posted something from the southern hemisphere, so for most of the watchers here, the trough and short wave would appear the other way around.

We done for posting it.

In my experience you have the main primary Low pressure system. A typical example was the one that steamed through last night through the S SW and Wales and cleared

away earlier today. Often in a zonal flow a secondary low pressure forms usually following a similar track - this is called a secondary low or depression. A trough is usually

characterised by a 'V' shape in the isobar chart on a map. On the ground a trough or cold front often marks the centre line of the trough, with typically enhanced showery

activity through to a band of heavy rain, squally showers and thunderstorms, and even thunder-snow in mid winter. A trough is not to be confused with a mean trough which is

altogether different and is used to describe an area between two defined High pressure system or ridges. A short wave finally is often a smaller low that spins off a primary

low pressure usually from the edge of a warm front or the main low pressure system itself. Its often where the main low has left the jet stream and become slow moving, (as was the case a lot earlier this summer in the UK ) and a smaller disturbance breaks off, and gains a small rotation and separate identity to the primary low pressure system.

I'll be honest mate, I couldn't find any Northern Hemisphere charts to use. Although it should be the other way around which I knew about, the characteristics remain the same however.

[The Eagle]

Possible snow in the west on the ECM @ 96 hrs?

Edited November 25, 2012 by The Eagle

[Jonan92]

ECM is a disaster

Edited November 25, 2012 by Jonan92

[The Eagle]

Not good at 120 hrs for prospects on the ECM.

[Snowstorm1]

Possible snow in the west on the ECM @ 96 hrs?

ECM is a disaster

Confused conflicting opinions again

[SMU]

We are going to have a MASSIVE split tonight-

ECM poor. UKMO & GFS excellent.

HUM-

stay on the fence im afraid.

S

[Swave Snow]

ECM is a disaster

Please care to explain WHY?

[chionomaniac]

ECM T+120 seems to be following the minors with the block sinking and energy crossing the Atlantic

[January Snowstorm]

Looks ok to me at 120hrs, though next frame is key

[Chris D]

Looks like I'm eating my hat then.